This invention relates to record disc playing apparatuses capable of automatically cancelling inside force on their tone arms, and more particularly to a record disc playing apparatus adapted to automatically cancel the inside force continually in an appropriate manner in accordance with the rotational angular position of its tone arm.
In general, in a record disc playing apparatus of the type having a tone arm supported so that it can rotate about a vertical pivotal axis, as the tone arm moves in swing rotation, a tracking error of the stylus of the pickup cartridge mounted on the outer end of the tone arm relative to the record disc arises as a natural occurrence, and a distortion is introduced into the reproduced signal. Accordingly, in order to reduce the tracking error angle to minimum, the tone arm is provided appropriately with an offset angle and an overhang, as is known.
However, in a tone arm having an offset angle as mentioned above, an inside force arises, as is known, and, as a consequence, there are caused adverse occurrences such as increase of the distortion in the reproduced signal, lowering of the tracking performance, and abnormal abrasive wear of the stylus tip. The magnitude of this inside force is substantially proportional to the stylus pressure up to a value thereof of approximately 3 grams (g.).
Accordingly, measures and means for applying a force in the direction (outward) for cancelling this inside force to the tone arm, that is, means for accomplishing a so-called inside force cancellation, have heretofore been used. In one example of these known inside force cancellation means, the force due to a weight is transmitted as an outside force by a thread to the tone arm. However, the inside force varies with variation of the position of the tone arm relative to the record disc and, furthermore, changes also with the magnitude of the stylus pressure. As a consequence, in this known means for inside force cancellation, since the outside force applied to the tone arm is constant, it has been impossible to cancel accurately and positively the inside force continually varying with the position of the tone arm.